1. Field of the Invention
The invention relates to a driving apparatus for driving a driven device array in which a plurality of light emitting devices, exothermic resistors, or the like are arranged, an LED head having the driving apparatus, and an image forming apparatus.
2. Description of the Related Art
Hitherto, among image forming apparatuses such as a printer and the like, there is an apparatus in which driven devices (that is, devices which are driven) in an array shape, for example, an LED (Light Emitting Diode) array is used as a light source, the LED devices are selectively driven, and an image is formed. In a driving apparatus which is used for such an image forming apparatus, in order to obtain an image of high quality at low costs, it is necessary to have a memory cell circuit for storing correction values to correct a variation in electric characteristics every driving device in an IC (Integrated Circuit) so as to drive each driven device (LED device here) by a uniform electric energy. A tremendous effort is made to realize storing means of the correction values at the low costs (refer to JP-A-2002-248805).
In such a memory cell circuit having the image forming apparatus in the related art, a plurality of dot memories (constructed by a plurality of memory cells) for storing, every driven device, correction values of powers which are applied to the driven devices are divided into a first dot memory group and a second dot memory group which are alternately distributed in layout order of the plurality of driven devices, the memory cell circuit has data lines which are individually arranged for every first and second dot memories and a common word line which is arranged in common for the first dot memory group and the second dot memory group, and the correction values are stored into the dot memories by using the data lines and the common word line.
In a multiplexer circuit which switches reading positions when the correction values are read out of the dot memories, the dot memories belonging to the first dot memory group and the dot memories belonging to the second dot memory group are connected as pairs in the layout order of the driven devices, and buffer circuits are provided in an input portion of the multiplexer circuit in order to prevent inversion of the memory storage data which is caused by data collision when the pair of dot memories are switched every dot memory and the data is read out therefrom.
There are the following main problems to be solved by the invention. In the memory cell circuit, the number of path transistors which are connected to the data lines arranged every dot memory is very large. The number of the data lines and word lines is large and a chip area increases. Thus, it becomes a cause of obstruction to reduction in costs of the driving apparatus. The invention intends to solve the above main problems and reduce the costs of the driving apparatus.